Polarizing plates have been applied to various image display devices such as liquid crystal display devices, organic light-emitting diodes and the like. A polarizing plate that is currently mainly used comprises a protective film laminated on one or both surfaces of a polyvinyl alcohol (hereinafter referred to as PVA) polarizer manufactured by dyeing a PVA-based film with iodine and/or a dichroic dye, crosslinking the iodine and/or dichroic dye with boric acid or the like, and aligning molecules in the film by stretching.
In recent years, the thickness of image display devices has been gradually reduced, and the thickness of the bezel and edge portions that do not display an image has been minimized in order to achieve a large screen size. In particular, various functions, including a camera and a video phone, are generally mounted in small and medium-sized display devices whose portability or mobility is emphasized, as well as notebook computers and personal computers (PCs). Specifically, components such as a camera are being mounted in image display devices. In addition, in terms of design factors, attempts have been made to impart various colors to product logos or bezel regions.
Meanwhile, conventional polarizing plates include an iodine and/or dichroic dye dyed throughout thereof, and thus show a deep black color, making it difficult to impart various colors to image display devices. In addition, when the polarizing plate is placed on a component such as a camera, there is a problem in that the polarizing plate absorbs 50% or more of the quantity of light, and thus the visibility of the camera lens is reduced.
To overcome this problem, during attachment of the polarizing plate, a physical removal method can be used in which a portion of the polarizing plate, which covers the camera lens, is removed by a process such as punching or cutting. Alternatively, a chemical removal method can also be used in which the polarizing plate portion that covers the camera lens is removed or bleached with a chemical substance such as an iodide ion.
However, the physical method as described above can impair the appearance of image display devices, and damage the polarizing plate due to the characteristic of the punching process. In addition, in the process of physically removing the polarizing plate portion as described above, a problem may arise in which the polarizing plate is torn. This problem is becoming more severe, due to a recent trend in which the thickness of polarizing plates has been gradually reduced. Meanwhile, in order to prevent damage (such as tearing) to polarizing plates, the punched portion of the polarizing plate should be formed sufficiently apart from the corners, and when this polarizing plate is applied to an image display device, there is a problem in that the bezel portion of the image display device becomes relatively wider so as to deviate from the recent narrow bezel design of image display devices. In addition, when a camera module is mounted in the punched portion of the polarizing plate as described above, there is a problem in that, because the camera lens is exposed to the outside of the image display device, the camera lens is likely to be contaminated and damaged when the image display device is used for a long period of time.
Meanwhile, the latter chemical removal method has problems in that it is difficult to accurately remove iodine from a desired portion of the polarizer, due to the diffusion of the chemical substance used, and thus it is difficult to control a depolarization region, and in that the chemical method is difficult to apply to a polarizing plate having a protective film bonded thereto.
Accordingly, there is a need for the development of a novel process that overcomes the above-described problems and that is used to locally form a depolarized or polarization-removed region in a polarizing plate so as to have a suitable size required.